This invention relates to an extendable exhaust nozzle for rocket motors. In a more particular aspect, this invention concerns itself with a system for deploying an extendable rocket motor exhaust nozzle or exit cone.
With the present interest in the operation of space vehicles, considerable research has been conducted in an attempt to increase the overall efficiency of rocket engines. One area of particular interest is the rocket engines' nozzle or exit cone. It is well known that an increase in the area ratio of the engine nozzle throat to the area of the engine nozzle exit cone will increase the performance of a rocket engine since it allows the exhaust gases to drop as close as possible to the ambient pressure outside the rocket. When a rocket is fired in the earth's atmosphere, particularly near sea level, the rocket nozzle does not have to be very large because the pressure drop to ambient pressure occurs very rapidly and efficiently in a short nozzle. However, when a rocket begins to operate in the upper atmosphere, the pressure drop to the ambient pressure surrounding the rocket becomes much more difficult and therefore the nozzle must become much larger in size in order to be efficient.
In order to solve this problem, several methods of expanding or extending the nozzle have been suggested. However, if the existing nozzle structure of an engine is simply extended to produce a larger area ratio, the extension in some instances would interfere with components, such as propellant tanks, of the adjoining stage of the space vehicle. Thus, what is required is a nozzle that can be stored in a compact or non-extended condition and then deployed to its extended condition at a predetermined time to increase the operational efficiency of the rocket engine.
With the present invention, it has been found that rocket engine exit cones of the extendable type can be stored and then extended by a system which provides for coating, plating or bonding a particular nickel-base alloy, referred to as Nitinol, to the interior surfaces of the engine's exit cone. This particular alloy exhibits the unusual property of "mechanical memory" and it is this property that provides the unique means for deploying the exit cone to its extended position. The invention provides a novel means for deploying extendable rocket nozzles or exit cones and entirely eliminates the complex and expensive mechanical deployment schemes utilized heretofore.